I use lindexed with the API key. It definitely helps because it has a 100% crawl rate with the google bots, and that's the first step in indexing. Then after a few weeks I throw it into GSA Indexer, and then when I feel motivated, a large scrapebox run.
As far as tests, that is an extremely difficult thing to answer because as you know indexing occurs naturally over weeks and months. So you need to factor that out somehow, and it isn't very scientific, because the results are convoluted.
I can tell you for a fact that two weeks ago I ran a file of about 10,000 through SEO Indexer, and within 3 days, 25% were indexed. Now that is a short timespan in which to measure indexing, but I can tell you that 0% to 25% in three days is outstanding. I didn't follow up after that because checking on the indexing again on a list that big is a pain in the butt.
@sonic81 - Bing and Yahoo favor older more established sites. So you can be at the top in Google for a very competitive phrase with high volume, but if your site is <1 year old or thereabouts, you won't see the good rankings in Bing Yahoo. Bing Yahoo also loves a ton of links direct to the moneysite, but if you do that, you will tank in Google. Like @Brandon, I don't check Bing Yahoo anymore.
@thisisalex - Your priority should be tier 1, but you do want to make the effort for lower tiers. It does pay off.