Hi, I have an Ellison EFS-5 on my O-360-A1A powered RV-4 (an EFS-4-5 is recommened, but I got his one 2nd hand and thought I would try it). I've posted on it a couple of times if you know how to do a search you will find them. The Ellison does allow me to lean further than with the old carb, and works inverted great. Hand starts are also quite easy and reliable. I added a Van's solenoid primer kit when I changed to the Ellison, as I relied upon the throttle accelerator pump on the carb for cold starts before that.
I used the FAB airbox and filter I had on the carb. I made a new top plate for it though, with a bell-mouth extension that bolted up to the TBI inlet. This kept the air intake of the FAB in the same location as with carb and meant I didn't have to re-do the cowl air inlet. Read all the tips and FAQ from the Ellison 'site when planning the changeover.
I installed a vapour return line originally, but later removed it with no ill-effect (Ellison does not recommend one - I should have listened). When hot on the ground the engine will 'burp', due to vapour formation I presume, but it clears with power and I have never experienced it in flight. I have cool air blast tubes directed at my maggies and fuel pump, and no gascolator.
Setting up the TBI to begin with is easy enough, the instructions are clear, but some further adjustment is often required to get the balance between idle, idle cut off and inflight mixture is required.
I think they are a good thing, FI is also a good thing, but heavier and dearer.