I flew the Island Hopper (UA 154) o/w on Feb 11. Spoiler alert: This review is not as positive as the ones posted elsewhere in this thread.

Overnight in HNL
Facing this dilemma, I stayed overnight at the Royal Grove on Waikiki Beach for $80. A relatively good deal. a/c worked well, & hotel was easy to find steps from #19 bus from HNL. The 1st bus departed at 04:00 am, plenty of time to get back to the int'l terminal - 3rd stop (@ 5:34 am) and visit the UC lounge (which conveniently opens at 05:00 am).
HNL-MAJ
On check-in, I discovered that UA 154 was not stopping in KSA! Since when? I (for one) did not get a schedule change notice!

I was not prepared (from reading the reviews) for the 1st leg, which is 5 hours in duration. Moreover, the pushback of UA 154 was delayed by + 1 hour by baggage irregularities (more on this later). During the delay, all 6 MAJ-bound infants on board wailed non-stop. Quite the experience! On a more positive note, the FAs served a full cooked breakfast en route, plus 2 drink services (more on the FAs as well later). Great pics from the left side of the 738. In MAJ, we were allowed to disembark with our carry-on, which I strongly recommend to anyone flying this route. T-shirts, crafts & beer for sale in Majuro Airport transit area. Don't even think about getting a passport stamped - its not happening. In the transit lounge, I saw a table full of UA bps. I approached the agent, and learned these were for residents traveling on a pass. Where we they going? For the most part, to MNL for medical treatment. Why MNL? According to my source, the medical care is better there than in HNL!

MAJ-KWA
The next leg to Kwajilein was a brisk 46 minutes. KWA is a "restricted US military garrison" i.e. you are not allowed to disembark, unless (of course) KWA is your final destination. Lots of US Army types disembarked - 32 in total (all, strangely in plain clothes). Taxiing for take-off, I spied a nice looking golf course in the restricted area alongside the runway. A nice perk for Army personnel? The only person to board in KWA was my seatmate - a Christian teacher who lives in GUM and spent his entire career teaching in Christian schools in KWA, PNI, & TKK (NB his favorite was PNI!)

However, pushback was again delayed by more than one hour. This time, the captain said he was waiting cargo checks and for performance numbers from Chicago! (Question - Is UA so centralized that a pilot crossing the int'l date line has to wait for orders from HQ?) I checked on united.com, and sure enough, UA 154/155 has a spotty on time record. e.g.
UA 154 Feb 12 Arrived GUM 59 minutes late
UA 155 Feb 13 Arrived HNL 47 minutes late.
Was the KWA stop eliminated to improve the O/T performance? If so, note to Jeff - the solution is not working!

KWA-PNI
The 738 on this leg is half-empty. The 1 h 27 minute flight plan is spent mostly in my seat with the seat belt sign on as we fly through storm clouds. According to my Christian seat mate, PNI gets 300 cm of rain a year, and has the highest elevation in the Marshall Islands.
At this point, certain aspects of the Island Hopper start to bug me:
- the IFE is lame, and I am now seeing the 3rd repeat of Anthony Bourdain's stories of the Civil War (why are we showing this to the Marshall Islanders, by the way?);
- there is no flight map on the 738, which I would find useful to identify other atolls on the route. Nor is there Channel 9 to listen to;
- there is no E+ seating on UA 154. Why?
- there are a record 5 FA's on board, and I swear at least two of them are incompetent to fly a mainline route. One (Mr. Casanova) spends the entire flight making eyes with his girlfriend on board. I am certain he cannot speak English. Another (Patti) only works the MIH-HNL based?

PNI-TKK
The FA's are now serving the 2nd installment of chicken sandwiches. Seriously, how many were loaded by catering? TKK is eagerly anticipated by the scuba divers on board, one of whom I met in bound on my SF0-HNL flight on Feb 10 (He ended up spending the night in HNL Airport, which - he said - was not that bad!). This is also the 1st leg where buy-on-board alcohol is for sale!


TKK-GUM
The last leg is predictably 1 hour late. I found it hard to re-set my watch on the MIH, as there were so many time changes. My cnx. to KOR was on time, so I had to scramble to clear GUM customs and get to Gate 10 for the full flight to KOR. I wondered what happens to others who miss their cnx? (Hanging out in the UC lounge is not an option as it closes at 19:30).

My Synopsis

While I enjoyed the MIH, I would have been a bit disappointed if my journey ended in GUM. KOR was a great place to overnight (albeit expensive) and the other option which looked worthwhile was TKK. (GUM is both expensive and disappointing according to other threads, notwithstanding the current article in Hemispheres trumpeting its emerging tourism sector).

I was unpleasantly surprised by the KSA flyover (once per week), the poor O/T performance, and the focus on cargo as a priority over passengers). I was also very disappointed by the in-flight experience i.e. set your standards lower, and you will not be disappointed!

Feel free to PM me if you have any questions.