Xohm appears to be living up to its billing as a much better network performer than the best the US mobile operators can offer. I haven’t tested Sprint’s mobile WiMAX service personally, so I have had to rely on blog reviews to gauge how well the service is faring since commercial launch in Baltimore on 29th September, but most of the reviews seem favourable so far.

By all accounts, Xohm customers are indeed managing to receive the advertised downlink speeds of between 3Mbps and 5Mbps, as well as between 1Mbps and 2Mbps on the uplink. The absence of any heavy and sustained Xohm-bashing in the blogosphere can only be reassuring for WiMAX supporters.

True, it’s still early days. Given the lack of Xohm marketing undertaken by Sprint, and the fact the Xohm-branded device range is still limited, it’s hard to imagine that Xohm’s back-office operations have been stretched to the limit. And Sprint, understandably, will have gone to great lengths to ensure its initial coverage area is well populated by base stations to give the best chance of achieving the top-end Xohm speeds for users coming onto the network for the first time.

The challenge for Sprint as more users come onto the Xohm network, the device range widens and the coverage area expands, is to maintain the network performance levels achieved in Baltimore.

That’s not to say Xohm has been free of criticism. A much shorter battery life for WiMAX-enabled devices compared to wifi (reportedly up to 50 percent shorter), as well as a difficult-to-use GUI to log on to the Xohm-network from devices running on Microsoft OS, have all been raised as shortcomings.

The lack of a round-the-clock Xohm customer helpdesk is also cited by one reviewer as a major drawback, but this seems harsh. The very early adopters of Xohm may indeed be more nocturnal than the average consumer, but you would suspect that the Xohm helpdesk opening hours of between 7am-11pm on weekdays (and 10am-9pm on Saturdays and Sundays) would be sufficient in most cases.

And anyway, the whole point of the Baltimore launch, besides showcasing the mobile WiMAX technology, is to iron out the inevitable service-provisioning, network performance and customer support wrinkles before expanding into other markets.

Just as importantly, the Baltimore launch can also test how attractive the tariff structures and prices for the Xohm service are. From the outside looking in, the introductory Xohm offers look very, very competitive. There are no long-term contracts and the monthly package is $30; a ‘day pass’ is available for $10.

It all looks very customer friendly, but there has been one fly in the Xohm marketing ointment. Although the service was initially pitched as offering unlimited data usage, it has subsequently come to light that Sprint has an ‘acceptable use’ clause written into Xohm subscriber agreements, which can be used to stop customers getting a ‘disproportionate share’ of capacity. It will be interesting to see how that plays out practically, but, despite this question mark, Xohm still looks attractively priced.

AT&T Wireless, for example, introduced its latest (and smallest) USB dongle last month, which can access its HSPA network. The dongle is ‘free’, but only if the customer signs up to a two-year contract at $60 per month. AT&T says that customers, typically, will be able to receive between 700Mbps and 1.7Mbps on the downlink and 500Kbps and 1.2Mbps on the uplink, but this is much, much slower than Xohm. And the two-year lock-in sounds even more onerous now that Xohm has come up with monthly and day-by-day arrangements for broadband access on the move.

Assuming that Xohm gains momentum, it’s not hard to anticipate that the likes of AT&T and Verizon will have to revisit their tariff strategies. Long-term contracts are already looking outdated.