Originally booked on NW flight today from FWA-DTW-TPE. Due to aircraft maintance, my FWA-DTW flight cancelled. After requesting that I must arrive in Taiwan Friday night or Sat morning (dah...otherwise, I will miss the presidential election in Taiwan and hence why will I even go), I was rebooked on CO through CLE and SEA. Of course, SEA-TPE leg is operated by Eva Air.

My original ticket is a full Y fare with mileage upgrade to WBC on NW. I am rebooked on Business Class (Z) on Eva, but the quality is just simply different. Furthermore, I paid close to $3,000 on my NW ticket plus the miles and if I were to buy the Eva Air ticket on my own, it would've only cost me about $2xxx for business class and $1xxx for Y class with mileage upgrade to business. The rerouting also makes me arrive in Taipei 8 hours later than my original schedule.

Now, I am going to write to NW and ask for something. For once, the new "business class" they rebooked me on is of total different quality than WBC (WBC is really first class quality and not the same as business class from a Taiwanese airline...). And I am also arriving 8 hours later due to NW's fault.

What's a reasonable amount to ask? I am thinking I want to at least get the 15,000 one-way upgrade miles back and possibly some compensation for my 8 hours delay and now being stuck in Cleveland airport for 6 hours...

I'd guess you were expecting to be on NW69 DTW-KIX-TPE .. now looking at BR25 SEA-TPE .. arriving 8hrs later @ 6.40am ??

Couple quik 'lemonade' thoughts:
I'd be on the phone to NWA about the upgrade miles before you leave CLE ~ sounds like you've got some time ! Getting your complaint on the record (noted in your PNR) can't hurt your case.

Down the road, if another MX crops up, you may be in a position to declare 'trip-in-vain' and bail out altogether, if you're so inclined = fat refund.

Apology miles/vouchers on an Intl itin: not in my area of expertise, but should be yummy ~ others will surely be along to opine.

Good luck.
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TTU will never give refund on fare difference. You might be able to get enough mileage for a free RT to Asia or a e-credit voucher. The most I've got was 25K miles for a serious misconnect (Feb snowstorm stuck in LGA and missed MSP connection to HNL; had an 18hr layover before HNL-NRT-SIN; forced MSP overnight and cannot retrieve checked baggage; gate agent gave me wrong part of hotel triplicate voucher and had to pay out of pocket; continued MSP-NRT-SIN).

Best way to calculate how much you are compensated: US$0.01 for every mile you are given. I usually take the e-voucher to offset my next trip.