Its worth every penny if you want to improve. I found that my LT was MUCH higher than I could have imagined and now my training zones are in line with what I should be doing. If you have the cash....do it.

I think the real question is are you just trying to get smarter or "real" serious because quite honestly you can do a simple test to get into the ballpark for what your VO2 max is by following the 1.5 mile test in the Triathlete's training bible or others I have seen online. Is it 100% accurate? NO, but then I refer back to the original question. Do you just want to get a ballpark estimate that you can check periodically to see if you are improving or do you want to drop ~100 bones every month or two. I like to keep track of my body fat score, but I'm not going to pay for a float test to get an accurate score either.

As far as the HR training goes, here is my .02 worth. I too am in my 2nd year of training and would like to see some serious improvements. I decided to try and use the other half of the $200 garmin I bought and actually strap the HRM on for a change. I also used the Mark Allen 180 - your age method and added two because I felt I was fairly active coming into this season. The score I use is 143 to be the top of Zone 2. When I first started I hated it, I felt like there had to be something wrong with my HRM. I would start running at 10 minute mile pace and my HR would shoot up over 150 and sometimes into 160 range. I would slow to a walk and my HR would drop down to 110 pretty quickly. I spent more time fudging with the HRM than actually performing the workouts or so it seemed. It may have been the most frustrated I have ever been working out, but I plugged away at it and slowly things started shifting and my HR started flatlining at about 140 +/- a couple. Tonight I busted out 5 miles at 8:00 minute pace and felt great. My HR never jumped over 145. Every time I looked down at my HR there it was at 140 - WOW! In 6 weeks I have been seeing noticable improvements using my HRM as a tool and I'm pretty juiced about it.

I am relatively new at this and was told to do base training at moderate HR, so used the Karvonen formula. Based on previous experience, it seemed closer to accurate than straight 220-age. I also found at first that it was hard to stay low, but that improved, and it gives you something else to look at during an indoor training ride (how your number changes based on what you do).
I hadn't been considering testing, but I heard about a study being conducted by some grad students in exercise physiology at UVA, so I signed up. There's no compensation, but I will get all of my info at the end (and there's food after you finish each time). I had the first session yesterday. This study looks at how a mystery Gatorade-like beverage affects your performance and all the parameters, so I had to not eat for 4 hours before my appt, which was 5 hours before I got on the bike, so that sucked and was probably different from a normal test that you might pay for.
Anyway, apparently most of the subjects before me had this same experience: sky high blood pressure before the testing, and perfectly normal afterwards. I think this is in anticipation of mainly the IV line being in your arm so that they can get blood while you're riding (which you can't feel at all once it's in). Also anticipation of all the other stuff: BP cuff on the other arm that keeps inflating, very cumbersome mask on your face, stickers all over your chest and a heavy belt keeping all the ECG leads together. In spite of the BP, my HR was normal resting before getting on the bike (all I saw before they blinded me to all the info). I don't know if that kind of anxiety affects blood parameters.
I was fine during the test but I wonder if that happens in tests that you pay for and whether it affects the results. They probably deal with it in some way.
In any case, I'll be very curious to see how the actual numbers compare to the estimates I've been using. A side benefit to this is that they have a BOD POD body composition machine. It's supposed to be accurate (I guess I could compare the actual results to a BMI calculation?). I also did a lung volume test in it. When I get all the numbers out, and if the people don't tell me that they had to throw out all my data because it was bad or considered unreliable for some reason, and if it's remotely interesting, I'll post about the relationship between direct measures and estimates.

--M