I would say it is definitely worth the $$$.

I don't have the EPSi - but I have a 2 Notes Torpedo - which I've loaded the same IR package into and am using it the same way as Ross is.

I downsized to a Zoom G3X (looooooong story) as my primary modeler. My rig is:

guitar -> G3X -> Torpedo -> M9 -> PA

I am using the G3X for a wah, drive pedal and amp model. The Torpedo is using the same IR Ross is talking about. M9 for effects/lead boost.

Before the IR - I was pulling EQs from wherever I could - a couple in the Zoom (pre and post amp model) and from the Torpedo (it has a five band graphic EQ) in attempt to dial the tone in - always tweaking, adjusting, never quite getting there.

Since the IR - I just play. No EQ except the amp model tone stack - and it just sounds/feels/responds like my rig back in the tube amp days. There are several that have risen to the top of my "favorites" list. They take all the guess work out of it. It's easy... pick a speaker cab that you might have selected in a real cabinet - match up the preamp - and get back to playing rather than tweaking.

Actually, I do still tweak - but now to get greater breadth of presets. I dialed in a dozen or so - and even with the "do they still sound good the next day, and the day after, and the day after" smoke test - still makin me smile!

For me - if I didn't have the 2 Notes Torpedo CAB I would definitely get the EPSi - and the Ownhamer IR pack (or whoever your favorite IR provider is).

Just my $.02 worth... but I was really surprised... pleasantly so.