Guildwood is a nice area (with not-so-good restaurants from what I hear), but it's very far from downtown (> 20 km) if that matters to you.
If you work downtown and don't mind taking GO, then that may be OK, but if you drive downtown during rush hour then it will be a major PITA.
I briefly considered it, but decided I couldn't deal with that much time in traffic every day. (I don't work downtown, but getting to or from Guildwood during rush hour would still have been far too long for my liking.)
EDIT:
What I might suggest you do is take transit or drive (depending on what you will be doing on a daily basis) to or from your workplace a few days from Guildwood, during rush hour to see what it will be like. When I bought my place, my cutoff was 30 mins driving. Guildwood would have been more like 45.
The Sunday-afternoon-drive-to-check-out-the-house is very misleading. I live < 20 minutes from downtown on Sunday afternoon, but 30 minutes away during rush hour, or sometimes longer like when it's raining. After about the 30 minute mark is when I start getting really irritated. YMMV.