1. It's great. If there's a charge in the rod, there is really no reason not to use it at the start of any moderately threatening fight.
2. According to LearnDB:
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Evocations skill and rod enchantment increases its recharge rate. A +0 rod with no skill gets 1 mana per 25 typical turns. Taking that same rod to +4 will double the recharge rate, 8 triple. Evo skill increases recharge rate by 1/turn for every 1000 skill.
Casting a spell lowers your nutrition by an amount varying with the spell's level: (1) 50, (2) 100, (3) 150, (4) 250, (5) 400, (6) 550, (7) 700, (8) 850, (9) 1000. This amount is lowered by the product of your Intelligence and Spellcasting. (For rods, your Evocation skill * 10, with a minimum of 5.)
So it's kind of similar to how training Spellcasting boosts your MP regen (by raising max MP, which is what regen is pegged to) and lowers spell hunger -- but here spell hunger matters even less than for conjurations-heavy characters, because the rod's limited MP pool and slow recharge rate means you are casting less frequently. Personally, if I had a stack of recharge scrolls, I would burn some of them on this rod as soon as there was a situationally-appropriate opportunity (i.e. drained it in combat and have a good reason to use it again immediately). And I would put points into Evo (but probably not prioritize it over my core skills) until I was happy with the recharge rate, which is a totally subjective thing based on how often I think "dang, wish that rod had recharged more".