Just a brief overview of what I think of the professions.
Inscription. I love this profession, I have it on 3 toons now, 2 of which are maxed. Yes, getting to max level takes a very very long time (as far as doing the NR inscription research, it will take months to learn everything). However, this is such a huge gold maker you make over a thousand gold an hour on both of my servers. Leveling is good too, you get access to buff scrolls and recall scrolls, so you have 2 hearths every 30 min. Overall very fun profession.
Jewelcrafting. Well, this is pretty horrible to level up. I must say I was surprised as the absolute lack of useful items while leveling. There are a handful of leveling rings/necks that are nice, but usually they are too little too late. However, at end game JC really shines, especially with the epic patterns. The dailies are an absolute pain though, this makes this profession far harder to truly master than others.
Engineering. I just leveled this a few days ago. I love it, i think it would be good for leveling. So many fun options, and great recipes abound. In BC/wrath there are some nice leveling items, including an ilvl200 helm available at level 72.
Tailoring. Easy to level, but you burn through gold. You'll get it back with bags though. Pretty good at endgame, esp BC and wrath have some nice leveling gear. I'd like to see even better gear though.
Leatherworking. Pretty much like tailoring, but more painful! If you dont have skinning or access to a skinner, in some spots its very difficult. A few hidden gems in this prof, and generally pretty hard to make money with (although each prof has nice end game items, the markets are obvious and saturated).
Alchemy. Fun again. So fun, after dropping 450 alchemy on one toon (pre-epic gem xmute), i picked it up again on another toon. The xmutes make this an easy 100g a day gold mine, and everything else is good. There is one spot that is a lose leader, but my 2000g investment I recouped most of it within a few days. I love the discovery aspects of it too, and the specialization is not yet worthless. Woot. This can rival JC or inscription for profit.
Enchanting. Its one of those long slogs. In BC it gets good, but before that, this is a huge gold sink, even w/ leveling. There isn't nearly enough greens while leveling for this to be breakeven. The armor/weapon vellums go a long way though, and due to those this can be profitable, but its a ton of work. Still, there are a handful of enchants that always sell (mongoose, +4 chest, etc). Enchanting in BC was horrible because of all the rep requirements and most of the good recipes were rare random drops from instances. Can you say kill me now? Since the 100% drop rates of BC raid bosses, it makese getting mongoose pretty easy. This issue didn't occur in Wrath, and instead almost everything is bought from a vendor using enchanting materials as currency. I think this is a great move and I finally feel that my max level enchanters are useful, if only for equiping alts. Also this was a major source of profit due to the saronite shuffle, before economies were brought to their knees.
Blacksmith
Actually pretty fun and useful. I haven't gotten this past 150 but already I can see some use out of it with the sharpening stones and rods. However this is significantly more expensive to level than other professions in terms of material and time. From 1-75 you need some 200 copper ore, which is not really realistic given the faster leveling times. This costs are going to have to go way down for cataclysm. For end game, I can see it being a money maker. If i had a nickel for every 'need BS for saronite swordbreakers' i'd be a rich man.
Mining/Herbing/Skinning
As a game with 3 gathering professions, all of these are good money makers and I wouldn't change it. If you start in a new realm with nothing but a level 1 and herb/skin, by the time you are level 10 you should have enough to buy 4 netherweave bags, by level 20 easily enough to afford your mount, and by level 60 easily enough to afford your flying mount. In northrend as of now herbing makes 500-1000g per hour (less now bc of the frost lotus prices decrease). This is in line with the top end professions such as inscription. So it's quite lucrative for these professions as it is, and if you thrown in the inate bonuses (stam/healing, etc), these are very solid and very easy to level professions. The one thing I can see is that in the mid-zones ie level 20-60 keeping up the professions can be hard, since you fly through everything so quickly.
