I would like to share my own thoughts on LoL/HoN:
It seems to me that what HoN fans say makes LoL a "casual" game is exactly what makes LoL more fun. No denying means a less tedious lane. Higher damage towers makes tower diving that much more rewarding. I find no gold loss on death more of a nice difference that doesn't really affect gameplay too much.
Also, at higher levels I believe LoL is just as competitive as HoN. Huckbuck says HoN has more elements where skill and awareness play in, but I think both games have these elements about equally. Where HoN has long stuns, lots of kiting, and juking through trees that allow you to show off your skill, LoL has way more skillshots and shorter cooldowns, as well as brushes that you can hide in. Positioning in both games is also quite important. Personally, I much prefer LoL's hero designs to HoN's, and also that each champion has four active abilities, plus a passive and two summoner skills. There's also just a subtle difference in design between HoN's heros and LoL's; stuff like more passives and longer cooldowns in classic DotA heroes, and also a greater reliance on items with active abilities.
I will say there are a lot of things I do miss about HoN; or, really, what I miss about DotA. It feels to me that S2 has turned HoN into an unbalanced mess. The new heroes they release don't seem to have the same feel as original DotA heroes did. There were a few that I felt were good, but most of them seemed like a mess of random nukes and overly complex abilities. Also, is it just me or is the new HoN shop interface a piece of ****? I am definitely looking forwards to DotA 2 in this regard, and also to play all the old champions that were never ported over the HoN (<3 Fuzzy wuzzy & Meepo).