Small two-octave keyboards are sufficient for most electronic music needs. For many years I have used my Novation BassStation shown in the second pic as a master keyboard to control my setup. If you make techno-ish music like me, triggering drums, samples, sample loops and the occasional chords is all you need so two octaves are enough in most cases, and you could always switch octaves live or for recordings like OrochiEddie mentioned.
Nowadays I use my Yamaha YS100 (61 keys) as a master keyboard.
When I started making music, I had a full-sized 88 key Roland JV-1000 workstation, it was a great piece of kit but way too large and heavy for gigging so the BassStation came in handy to replace it for that purpose. Bought it in '94 and it arrived two weeks before a gig I had in Hamburg, had to take the plane to get there and it would have been a nightmare lugging that big-ass JV-1000 around.
complexz, nice to see you've bought a FB-01, it's one of the best synths bargains you can make these days. FM synthesis is a wonderful beast, it takes a while to become familiar with it but the tons of awesome sounds you can create with it are more than worth it. Bought my FB-01 for 40 Euro bucks, YS100 for 70 and YS200 for 75, that's only 185 Euros for a setup which blows most other systems out of the water, sound variety-wise. I hope that prices for used FM synths won't get affected by the current classic synth price hype, people these days are asking ridiculous prices for crappy gear only because it's old... fucking "retro" bullshit... and then there's the tiresome analog vs digital debate. Complete waste of time if you ask me.
Oh, and as you can see from the pics, I'm a proud (and long-time) owner of an Ensoniq Mirage DSK-8, it's the first model with Reed keybed and steel top. It was the first affordable sampling keyboard ever released in 1984 and I love its gritty and lovely strange sound a lot, you just can't beat the combination of 8bit samples and analog Curtis filters, makes my knob twiddler balls tickle. Yeah, it's not really intuitive to use to say the least... it has a two-digit LED display, data gets entered in HEX values from 00 to FF. There are dozens of parameters accessible via numbers like 36 (filter cutoff) or 50 (VCA ADSR), takes a while to get the hang of it but it's actually not that difficult as long as you keep a parameter reference sheet within reach, have a calculator with a HEX function and don't mind reading up on stuff like Nyquist frequencies or input filter anomalies on certain sample time/rate combinations and how to avoid them...
...or to put it in the style of Zed from MiB: "The Mirage keeps us on HEX and standard 2x64k memory. Give it a few months. You'll get used to it... or you'll have a psychotic episode."