Connecting to a Johor Bharu flt. at 8:50 am
 

I will arrive at Changi at 1 am in the morning. Will it be feasible to take the first metro to Kranji (leaving at 5:45 am) and then cross over? How far is JHB airport from the border?
Thanks in advance for any info.

You're pushing it a little. It'll take you an hour to get to Kranji (with two transfers along the way), then bus to Sing checkpoint, Sing immigration, bus across Causeway, Malaysian immigration, and then a bare minimum of 30 minutes to Senai -- all told it'll be closer to 8 by the time you get there even if everything goes perfectly.

I'd suggest overnighting in JB (the border is open 24h) or taking a two-taxi combo instead. Standard reference for Singapore-JB-Senai connections:

http://wikitravel.org/en/Johor_Bahru

Also keep in mind that a taxi in Singapore isn't *that* expensive either - from Changi to Woodlands Checkpoint usually costs me about SG$20, so even with the 50% after midnight surcharge the worst you'd be looking at is SG$30 (or under US$20). From JB town to JB Airport a taxi will set you back RM35, or you can get the bus from JB town out to JB Airport for RM3 per person (which starts at 5:30am).

If you wanted to get a few hours of zzz's in then there's plenty of cheap options in JB town (the Compact hotel is my choice for a quick shower and kip, www.compacthotel.com.my - if you book on the AirAsia website you can usually get it for RM100 nett including breakfast, and it's about a 2 minute walk from the causeway - the common areas are pretty run down, but the rooms are decent enough). Otherwise you can head out to the airport early and crash at the Sofitel - they have rates from US$28+tax including breakfast on the website at www.accorhotels-asia.com and they have a free shuttle bus to the airport as well, takes about 5 minutes.

I would agree with GibSpmuh. Unless you are on an absoultely tight budget you should not take the MRT. You will really be pushing it time wise and as stated by the others, a taxi cab is not that expensive and will be much more convenient. Just calculate what a missed flight would cost you and the whole pic lightens up a bit ;) Cheers ...

Shuttle Buses from Kotaraya's Senai Airport City lounge leaves at 0530hrs / 0600hrs / 0630hrs / 0710hrs. The journey will take approx 40mins. Cost RM$1.

Kotaraya City Lounge is sited just behind the Pan Pacfic Hotel Johor.