I have both. Advantages/disadvantages compared to Google Apps:

+ Far more configurable

+ Sieve scripts

+ The web interface is faster

+ Easy to access their engineers (hang around on emaildiscussions.com)

+ The contribute to Cyrus, etc.

+ Family/business accounts where not everyone needs to be an an expensive tier.

+ Standard IMAP, so works a lot better with most clients.

+ Some Dropbox integration.

- Mail gets blocked more often (e.g. there seem to be ongoing issues with Craigslist).

- They don't support labels. If you have a label-driven workflow, you are going to be frustrated.

- Extra storage space is much more expensive than Google Apps (which has e.g. 1TB for $10 per month).

- No real 2-factor auth, there is always an account with full access. Not a possibility to make a restricted IMAP account.

- Obviously fewer apps than Google Apps.

- Relatively slow support times (though I have never contacted Google Apps support).

- The Google Mail client is still much better than the Fastmail client (e.g. reflowing text, when the internet connection is spotty).

o Australian company with servers in the US (and Iceland). So, no real advantage wrt. the NSA et al.

Great. The thing I like is that you get maximum flexibility, and good web interface. For example: I run a mail server which handles mail for some subdomains, and the root domain mail I route through them. Every time I give an email out to a company, I name it company-name@one-of-many-short-fastmail-domains.com. I never have to worry about spam from those email address, as I can filter and cycle those at will.

I do something very similar, but instead of using the company name (or something close to it) I use a long random string instead. It mainly prevents someone from 'company hopping' (i.e. changing 'facebook' to 'google'). The chance of that happening might be small, but I figure I may as well as it isn't really any more effort

I've used them since 2006. It's probably the only service I have never even questioned whether or not I should renew every year. It is very good.

I've never had a problem with them, and I've been a (paying) customer for over a year now.