I used an inline filter on a garden hose to fill up my 55 with no sump... That was before I had an RODI unit.
I am in the process of setting up a 120gal tank with a 40 breeder sump... Since I have the RODI unit now, I figured, why not use it? I DID want to test my plumbing (yeah, I'm no plumber, I definitely had some leaky pipes), but figured it would be best to use the RODI. I changed the DI resin before filling, and let her rip. Took ALL weekend to fill (running nearly 24hours straight), but I figure it's better to be safe than sorry. I'll probably still have some problematic algea to deal with, as all new tanks do, but it's something I can take out of the equation... If I had problematic algea and used that in-line filter, I'd always be wondering if it were because I didn't use RODI water to fill it.
In this hobby, limit your excuses...