The use of Roth IRAs is increasingly popular as a tax planning strategy, especially in the years since 2010 when the income limits on Roth conversions were lifted, opening up access to Roth conversions for anyone. And although the income limits from conversions has been eliminated, the ability to recharacterize a Roth conversion remains, no longer as a mere "undo" for an accidental conversion at high income levels, but now increasingly as a proactive strategy to convert and wait and see what happens with the investment; if it's up the conversion stays, and if it's down it's recharacterized to be converted again in the future (at a lower tax cost).
However, one significant caveat of Roth recharacterizations and this kind of wait-and-see-before-deciding strategy is that Roth recharacterizations must allocate gains/losses across the account on a pro-rata basis. As a result, one cannot simply "cherry pick" the worst performing investments from a Roth conversion to subsequently recharacterize, and trying to do so can accidentally shift originally-Roth investments into a traditional IRA in the process! Fortunately, though, a special rule allows Roth recharacterizations to occur on a standalone basis, as long as the conversion is placed in a separate account in the first place.
In fact, this "separate account" rule is so favorable, for larger Roth conversions it becomes another proactive planning strategy unto itself - instead of merely converting into a single standalone Roth IRA (separate from existing Roth IRAs), complete the Roth conversion one investment/asset class at a time into a series of separate standalone Roth IRAs (separate from any existing Roth IRA and each other). By doing so, the investor can actually see the outcome of each individual Roth investment, one at a time, keeping the top performer(s) and recharacterizing the rest, with as much as a 21-month time window to see the investment results before being forced to make a final decision! While ultimately the outcome of whether a Roth conversion is a good deal or not is still driven by tax rates, being able to know the investment results, and cherry pick the top performer after the results are in, can go far in turbocharging the value of an already-beneficial Roth conversion!