In reply to plexiglass_nick: Just back from Canada (Squamish) and climbed a few cracks. The main difference I feel between UK cracks and Squamish cracks are the footwork.
In the UK, you can generally get away with only the odd foot-in-crack move. Out there, some pitches (for example The Zip at 5.10a) are pretty thin hands, crack in feet the whole way.
I found corner-cracks much easier than face cracks, for exmaple, the Grand Wall is 5.11a and we found it ok, but it's mainly corner cracks and laybacking.
I did my first offwidth in Skaha, it was 5.10c and probably one of the most physically intensive 40m of climbing I've ever done!
After 3 weeks we still didn't have a good idea of the grades, and, we were told they are soft in Squamish compared to Yosemite!
If you have big plans, make sure you have time to build up to it. We got there after 4 weeks of solid climbing in Scotland and Norway, expecting to cruise 5.11a straight away and got spanked on 5.10c. By the end of the trip we were doing 11d onsight on bolts (face climbing) and 11b onsight trad (mainly thin corner cracks).
On final bit of advice. Learn to thumb stack. It's one of the most versatile jams there is!
Check my logbook for an idea of grade comparisons.