I set out in my current project to be Max only
Well, if you are talking using only the stuff that comes with BlitzMax then obviously you aren't going to succeed in all cases.
It's not like Python, which has everything but the kitchen sink included with the base distro.
I suppose it's a bit more like Perl, where you need to plug in extra functionality (perl mods) to do more stuff.
Not a big deal in the real world.
GUI knocked my tits in
With MaxGUI? I'm not at all surprised. For anything other than a basic window with some buttons, it is poorly lacking.
should I take the plunge and finally buy BlitzMax?
Well, it's not terribly expensive, and it's always fun learning something new, so why not? :-)