I've been a customer of mycustomtailor for probably two years now and accordingly feel I have an insight into the issues in this thread. Thus in the spirit of SF I offer some tips.
1. Measurements
I feel most problems arise because of bad measurements supplied by customers. I include myself in this - my first order was a suit from their cheapest range first and even though I had it altered locally and it's fine it's not as good as later suits when I altered my measurement profile. In fairness to mycustomtailor, they mail you to ask for feedback and welcome comments and photos after your order is sent so they can improve the fit (which usually means correct bad/wrong measurement). I'd strongly advise everyone who's considering using an online tailoring service to do three things -
a) to ask a friend to help take the measurements - there are lots (around thirty) of them
b) to doublecheck the measurements before ordering
c) to send a photo or two as a guide to body type and proportions
And, as I say, if there is a problem the first time, take photos and send them and re-check original measurements (there may be a problem on their side, but that hasn't, in fairness, been my experience).
2. Fabrics
It goes without saying that you should choose the 100% natural cloths, as is the wont of SF members. There are a few 'blends' offered on these sites that people of this forum would blanch at...
3. (The Devil is is the) Details
There's a good range of standard options offered - the usual canvassing, working buttonholes, combinations of pockets, choosing linings, lapel widths etc, but they also take other requests on board without a fuss (e.g. strange coloured stitching, diagonally-cut working sleeve buttonholes are some of my personal fetishes!) - and sometimes without extra charge. Of course, these are the kind of things which are the icing on the cake AFTER you're sure you've got the meaurements right.
4. Workmanship
I recently wore one of these suits (my fifth) on a visit to a local master tailor - and I mean 'master'. He's your classic old-school craftsman and doesn't 'believe in the internet'. He was amazed when I told him how I'd ordered this suit and I asked him for his comments. He said that his own preference and style was for a more natural shoulder (there is a little padding in the coat) and a tad more waist suppression, but that he wouldn't fault the workmanship in the least. I had expected that he'd be highly critical but he was very even-handed and gave praise where it was due.
Hoping this is informative and that it convinces other SF members that online tailoring can actually great results for some people!
Beau