In October, my colleague Dan Caplinger wrote about the biggest boon yet for investors: TD AMERITRADE's (Nasdaq: AMTD) entree into the fight for dollars in the exploding exchange-traded fund market. "Although TD AMERITRADE was slow to get into the game, it's fired what could be the winning shot in the latest battle over commission-free ETFs," Dan wrote.

The shot
TD AMERITRADE launched more than a hundred ETFs at no commission. Importantly, the ETFs spanned the universe of ETF companies -- iShares, SPDRs, Vanguard, to name a few -- bucking the trend of a discount broker partnering with a specific fund family.

Up to then, Charles Schwab (NYSE: SCHW) offered Schwab-branded ETFs at no commission, Fidelity offered 25 no-commission ETFs from BlackRock's (NYSE: BLK) iShares unit, and Vanguard offered its own ETFs sans the normal broker rake.

In more recent months, Scottrade unveiled its own line of funds, leaving E*TRADE (Nasdaq: ETFC) as the best-known discount brokerage without a horse in the race. (And with major ETF provider State Street (NYSE: STT) also on the sidelines, there seems to be a natural partnership opportunity.)

How's it working out?
When TD AMERITRADE Executive Vice President Peter Sidebottom stopped by Fool HQ earlier in June, we asked him how the company's ETF strategy has worked out thus far. According to Sidebottom, as measured by client satisfaction and money inflows, the program has been "tremendously successful."

In determining the company's ETF strategy, he said the decision came down to core values -- TD AMERITRADE has "a belief in open markets."

Plus, it's good business. In October, Dan wrote that not partnering with a single ETF provider could be "the winning shot." Sidebottom obviously feels that way, telling a small group of Fools that fostering an open marketplace with the best product is simply hard for a competitor to match.

Sidebottom said that on the retail side, for every $1 invested in a commission-free ETF, the company is routinely getting $0.50 or more in other assets. In the company's most recent quarter, it posted record trading volume and "gathered its highest amount of quarterly net new assets to date," reported The Wall Street Journal.

While it would be silly to attribute such results solely to the company's ETF strategy, that strategy does seem to have been a shot in the arm.

For more on brokerages or commission-free ETFs, visit our Broker Center today.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.